The present invention generally relates to implantable medical devices and implant procedures, including devices and procedures used to monitor physiological parameters of the living (e.g., human) body. More particularly, the invention relates to anchors for a medical implant, methods of manufacturing anchors, and methods of placing medical implants, wherein the anchors and methods are suitable for use in procedures performed to diagnose, monitor, and/or treat cardiovascular diseases, including congestive heart failure (CHF) and congenital heart disease (CHD), for example, by monitoring pressures in the left side of the heart.
CHF is a condition in which the heart fails to pump efficiently, and currently affects about 4.7 million patients (over 400,000 new patients per year in the U.S.). Estimates are that CHF accounts for about 5 to 10% of all hospitalizations and costs over $38 billion in the U.S. Following diagnosis of CHF, physicians typically monitor disease progression on a continuing basis to better tailor treatment. The best course of action for a tailored treatment involves monitoring pressures of the left side of the heart, particularly left ventricular end diastolic pressure (LVEDP, also known as left ventricular filling pressure) and mean left atrium pressure (MLA). These pressures are recognized as the best parameters for characterizing CHF in patients. Clinical evaluation of LVEDP or MLA is currently limited to cardiac catheterization procedures, which provide a snapshot of pressure data a few times per year at most, carries morbidity, and is expensive.
CHD includes various defects of the heart that are typically present at birth. A particularly complex example is a heart that has only one functional ventricle. In order to provide patients with appropriate solutions, multiple surgical procedures are required. These procedures enable the single ventricle to serve as the systemic ventricle, while the lungs receive blood flow via different anastomosis (for example, a Fontan baffle). A key dilemma in the treatment of these patients is the timing of the different surgical stages. The inclination is to perform the surgeries at a younger age. However, if performed too early, the outcome can be dismal. The hemodynamic status and timing of the different surgical stages can be assessed by invasive cardiac catheterization to measure pulmonary artery pressure and resistance. However, as noted above with respect to monitoring CHF patients, cardiac catheterization provides only a single measurement in time and has been associated with morbidity and mortality in CHD patients.
Using an implant to monitor pressures of the left side of the heart is very challenging for many reasons, most importantly the potentially fatal outcome of any thrombi caused by the implant. Miniaturized sensors capable of being chronically implanted are gaining particular attention, especially those made produced by MEMS (microelectromechanical systems) technologies. Notable examples include devices disclosed in commonly-assigned U.S. Pat. Nos. 6,926,670 and 6,968,743, and commonly-assigned U.S. patent application Ser. Nos. 10/679,888, 10/679,916, 10/679,926, 10/677,674, and 10/677,694, which collectively have achieved significant advances for the use of implants in diagnosing, monitoring, and/or treating cardiovascular diseases. When adapted to monitor pressure, the devices disclosed in these patent documents generally have two primary components: the implant comprising an implantable telemetric pressure sensor that is batteryless or makes use of a small battery, and a companion hand-held reader. The implant further preferably includes custom electronics for processing the output of the sensor and an antenna for telemetry and, if necessary or desired, for tele-powering the sensor. Telemetry and tele-powering can be achieved via various techniques, including but not limited to magnetic telemetry (including RF), acoustic waves, ultrasonic waves, with the currently preferred technique typically being magnetic telemetry. The reader transmits power to the sensor, and the sensed pressure is in turn transmitted back to the reader. Data collected from the sensor can then be used by a physician to tailor the treatment of the patient. In some cases, the implant may also be configured or adapted to perform additional functions, such as delivering a drug or an electric signal to the muscles/nerves.
In view of the foregoing, it can be appreciated that miniaturized implants of the types described above can provide chronic, continuous bio-pressure measurements and support the trend toward home health monitoring. Advancements have also been achieved in regard to the delivery and anchoring of such medical implants within the heart for monitoring heart pressures. Notable examples include delivery and anchoring systems disclosed in commonly-assigned U.S. patent application Ser. No. 10/730,439 and U.S. Patent Application Publication No. 2005/0065589. Nonetheless, further improvements are desired, particularly in regard to the reliability and manufacturability of anchoring systems and the simplicity of their delivery.